The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Historically, the standard method of sealing two joints not directly connected to each other has been to use a tube with an o-ring at each end. This design has been found to have two main deficiencies; the first being the seal's inability to compensate for offset between the two bores and the second being various assembly issues including missing o-rings, cut o-rings, rolled O-rings and overall labor intensive.
An improvement to this sealing solution was patented in Europe (DE19548249C2 and DE19902953A1) by FDS Reichelsheim by directly molding rubber to an adhesive covered tube. This technique allowed for large seal beads to be incorporated into the design which would allow for misalignment in the application as well elimination of the majority of assembly issues found with the tube and o-ring design. The deficiency with this design is the reliance on the adhesive bond between the tube and the rubber which has the bond failure modes already specified.
Current design tube seals are 100 percent reliant on rubber to metal adhesion for proper function. Adhesive to metal bond failure has resulted in field failures of tube seals utilizing straight wall designs. Several failure modes have been found to cause this condition including initial metal surface condition, inadequate metal preparation, adhesive thickness, adhesive age, adhesive “sweep” during molding and mold release “sweep” during molding. Adhesive “sweep” is caused by the injection of rubber into the mold that flows parallel to the wall of the tube and “sweeps” away the adhesive that is applied to the wall so that the adhesive is pushed toward the bottom of the seal.